1. Technical Field
The present teachings relate generally to solar energy collection assemblies and, more particularly, to hybrid photovoltaic-thermal collection assemblies.
2. Description of Related Art
Solar hybrid energy collectors, also known as photovoltaic-thermal (PVT) collectors, represent a new and growing field of energy generation. The combination of photovoltaic (PV) and thermal collection in a single unit provides a more efficient collection system than a collector that captures only electrical or only thermal energy. For example, conventional solar hybrid PVT devices may have efficiencies as much as three to four times greater than a typical PV-only system.
In addition, the thermal energy collected by a PVT device—energy that would otherwise have been wasted in a PV-only system—may be used constructively in applications including but not limited to water-heating, space-heating, low-temperature generation of electricity, and/or the like. Moreover, the removal of heat from a PVT device may be advantageous to its operational efficiency since cooler PV cells operate optimally at temperatures of less than or equal to about 25° C. By contrast, in a PV-only system, the build-up of thermal energy from overheated panels reduces efficiency and electrical output of the system.
Notwithstanding the above-described benefits of PVT devices, conventional solar hybrid energy systems remain complex, expensive to manufacture, prone to mechanical failure, and typically require trained and specialized personnel for their installation. One reason is that the use of liquids (e.g., water, halocarbon coolants, etc.) to cover PV cells and act as heat transfer agents in conventional PVT devices creates challenges for both installation and proper device functioning. By way of example, water is subject to freezing in colder climates, and halocarbon coolants (e.g., fluorinated hydrocarbons such as those sold under the trade name FREON by E. I. du Pont de Nemours and Company) may require special handling and recycling facilities.
An example of a hybrid system is disclosed in U.S. Pat. No. 4,700,013 (Soule). In this example, a PV collector absorbs short wavelengths and a thermal collector, which is placed below the PV system, absorbs long wavelengths associated with heat energy.
Another example of a hybrid system is disclosed in U.S. Pat. No. 4,607,132 (Jarnagin) in which PV cells are placed above a chamber containing a heat exchange fluid such as water or Freon.
Another example of a hybrid system is disclosed in U.S. Pat. No. 6,675,580 (Ansley, et al.), which discloses a flexible assembly of PV cells that can be attached to a solar collector below the PV cells.
Another example of a hybrid system is disclosed in U.S. Pat. No. 6,630,622 (Konold). The disclosed device uses a complex system of heat transfer tubes and Fresnel lenses in order to concentrate solar power.